3/10/09 FCST: IL/MO/AR/IN/OK/OH

[Scott Weberpal]

From what I'm seeing on the 00z WRF, tomorrow has gone to crap compared to what the 12z was.

12z had a nice zone of backed surface flow in central IL...no longer on the 00z. 12z had a nice bullseye of 180+ 0-3km CAPE around Peoria - that has been pushed south of I-70 on the 00z run. Surface based CAPE on the 12z run was 1000+, 00z run is roughly 500. QPF output on 00z WRF is completely linear before it gets into IL vs. somewhat broken on 12z.

The trend is not good, and given storm motion of 50+ mph won't be fun to try and chase either. More like take a storm, enjoy it for 10 minutes and go home. The only think keeping me interested in tomorrow is the forecast 0-1km SRH values approaching 200.

 

[Jared Farrer]

06z NAM and latest RUC are very troubling pushing cape values back some! And generally pushing times forward by an hour or two, which isnt a big deal. UVVs are there still but I think if we can get a few hours insolation it might change things.

One other thing is with this shear profile we could get splitting cells. With of course right movers being dominate. Shear isnt great but its enough with a little directional shear and alot of spead shear.

 

[V. Gensini]

Cannot wait to see the vissy sat this morning...There may be an OB left hanging around somewhere from this overnight junk...This set-up as a whole has lost some potential, but a boundary or two and some sunshine would certainly change things.

 

[Brian Emfinger]

Might as well add MO and AR to this. RUC, WRF, and 4km WRF are all showing storms developing along the front/dryline prior to 0z. Not expecting a lot out of this since things will go linear very quickly but with it being right on me I will be out.

 

[nickgrillo]

I haven't paid much attention to the setup prior to a few hours ago... RUC mesoanalysis shows the surface warm front extending from the surface low in northwest Missouri e/neward into Central Illinois. While total CAPE is progged to be fairly low -- i.e. <500j/kg sb/mlCAPE-- per both NAM and RUC through the late afternoon, 0-3km low-level CAPE is forecasted to be quite substantial -- i.e. >100j/kg -- in portions of the warm sector south of the warm front, which will help the potential for tornadoes with sustained convective cells given the strong low-level SRH in place. Strong deep-layer flow (i.e. southwesterly >80kts at 500mb and >50kts at 850mb at 00z) will provide substantial deep-layered 0-6km shear for sustained convection including supercells given the veering boundary layer wind profiles. Now, the warm front is progged to lift along/north of I-80 by 00z, with 55-60F tds progged to advect as far north as lower MI; assuming a supercell can become rooted within the boundary layer further north near the warm front and ingest the strong low-level SRH / relatively moist air parcels, then there will be a fair shot for a tornado or two (i.e. from central/northern IL into IN and perhaps even extreme southern lower MI). The most likely scenerio for today is strongly forced / shallow convection developing along the cold front around 21-22z and pushing e-neward into IL and IN through the late night hours. Given the incredibly strong deep-layer forcing and relatively moist low-level airmass across the warm sector, then perhaps convection can remain sustained enough to produce damaging winds / marginally severe hail as far east as central/southern lower MI between 02-06z (i.e. near the warm front and within zone of strongest boundary layer WAA).

 

[Andrew Pritchard]

Well, it's certainly not ideal but it's a short drive for me and my Tuesdays are very flexible, and since the long term models look very boring for a while I'll be watching. Now that I've convinced myself that I'm not TOTALLY wasting my time looking at data I'll get on with the forecast.

I'll likely be watching SW Illinois either along Interstate 55 near Litchfield, or slightly further south towards Highland along Interstate 70. Skies are more or less clear in southern Illinois and eastern Missouri ahead of the ejecting system. 0-3 km cape values will be around 125-175 j/kg in this area juxtaposed over areas of 300 m2/s2 low level helicities. With afternoon heating, we may even see surface capes try to reach towards the 1000 j/kg mark. Temperatures will likely be surging to the mid-upper 70s along Interstate 70 with dew points around 60. VV's really start spiking in eastern Missouri and western Illinois by 4 PM as convergence increases along the boundary. Hoping the strong forcing does not immediately lead to a forced line of convection, which it very well could. The plan will be to get on any storms pretty early while there is some discrete possibility.

Probably doesn't even qualify as a "good" setup, but I'll watch it and make the 90 minute drive should things start to juice up at all down there.

 

[nickgrillo]

Hoping the strong forcing does not immediately lead to a forced line of convection, which it very well could. The plan will be to get on any storms pretty early while there is some discrete possibility.

It probably will... In my opinion, the only area that has a truly fair shot at an isolated supercell is northeast OK into southwest MO. The other area would be further north near the warm front closer to I-80 between 22z and 01z, where perhaps there will be some potential for a shallow (mini-)supercell given the better boundary layer directional shear and associated richer low-level 0-1km SRH. Personally, I doubt the day will be much more than a strongly forced large-scale convective line.

 

[Andrew Pritchard]

The skies are very clear and temperatures have already soared into the mid-70's in SW Illinois. New RUC reflecting this and really increasing cape values in that area this afternoon.

http://beta.wxcaster.com/models/RUC/CENTRAL_RUC236_ATMOS_CAPE_06HR.gif

Surface winds are still going to be our biggest problem as things may still want to go linear. That said, the increase in instability due to more surface heating combined with decent 150-250 m2/s2 low level helicities could be doable for some minisupercells and a couple tornadoes in SW and SC Illinois. Will likely head out for that Litchfield / Highland target in an hour or so.

 

[Bob Hartig]

I'm not too excited about this scenario. Current surface obs and satellite suggest that any instability is going to be well removed from backed surface winds. I just don't see this setup producing. The winds are only going to veer increasingly as the surface low, currently positioned by IA/MN/WI borders, lifts northeastward. But since Bill and I are heading through the slight risk area anyway on the way back to Michigan from Joplin, I'll keep my eyes on the radar just in case.